Absorbent articles for personal hygiene are known in the art. Typical examples include sanitary napkins, panty liners, tampons, inter labial articles, adult incontinence articles, and baby diapers. Such articles are commonly used to absorb and retain bodily fluids and other exudates excreted by the human body. Typically, such exudates are perceived as malodourous and offensive. Therefore, methods and materials for controlling and reducing malodours in absorbent articles have been developed. Fragrance materials have been widely used for this purpose in absorbent articles, as well as ingredients such as silica or zeolites which are able to entrap some of the malodour generating molecules.
Other materials which are useful to improve the odour perception of absorbent articles are compounds that may or many not have a pleasant odour per se but which are able to improve the odour perception of the composition or article to which they are associated. Such materials may act, for example, by modifying how certain nose receptors perceive malodours, or by acting on the malodourous substance by chemical reaction, or complexation, or absorption/adsorption, for example.
In the present application the term “odour control material” includes any material which, as all those mentioned above, is able to improve the perceived odour of the absorbent article before, during, and/or after its use.
A large class of ingredients which is desirable to use as components of an odour control material for use in absorbent articles is that of organic compounds. In the context of the present application for “organic compounds” it is intended organic molecules which, introduced within an absorbent article, are capable to provide an improvement of the perceived odour from the article. Differently from inorganic components such silica, carbon black and zeolites which physically entrap malodours, organic compounds which are active on the odour perception of the user of the absorbent article, are directly active in modifying the odour of an absorbent article at any stage of use for example by providing a scent, by directly or indirectly reacting with malodorous substances (“indirectly” it is intended for example when an organic compound has an antimicrobial effect on microbes which generate malodorous substances) or by modifying the perception of malodours from the nose receptors.
Most organic compounds usable in odour control materials are volatile and tend to evaporate to some extent so that their amount in a commercial absorbent article is difficult to control. After the absorbent article is manufactured, the organic compounds start evaporating and, depending on the time and conditions of storage before its usage, a more or less large part of the odour control material will be evaporated and therefore not effective anymore.
Sealing the articles solves the problem only in part because a sealing which is compatible with the cost of such absorbent articles is usually not perfect and anyway a large amount of volatile odour control materials is also lost during the usage of the absorbent article also triggered by the body heat.
Odour control materials are instead most needed at the time when the absorbent article is loaded with bodily fluids, i.e. in the final period of its usage and during its replacement.
The most highly volatile odour control materials tend to evaporate in the first minutes of use of the article providing, for example, a pleasant feel during the process of wearing the article but no other benefits when, later, the article is loaded with malodorous bodily fluids.
In order to preserve volatile compounds for longer a successful route is to incorporate the volatile organic compounds into inclusion complexes of cyclodextrins (alpha cyclodextrins and/or beta cyclodextrins are examples of cyclodextrines which can be used herein). Examples of such complexes are described in U.S. Pat. No. 5,580,851 and in WO2008/104960 but any inclusion complex of a cyclodextrin with an organic compound can be used in the present invention. These complexes are very effective because they retain the odour control active and release it when they are wetted by the bodily fluids.
Inclusion complexes of cyclodextrin molecules are generally in the form of a fine particulate material which is commonly produced via spray drying of a solution containing the cyclodextrin and the organic compounds. It is believed that the cyclodextrins form the inclusion complex with the organic compounds and, when spray dried they prevent the organic compound from evaporating due to the chemical bonds formed with the complexed compound. When the material is wetted these bonds are weakened and the organic compound slowly released. Particulate materials are sometime troublesome to handle in certain manufacturing plants because of safety regulations which impose a very careful handling of fine powders, especially of organic compounds as it is the case with the inclusion complexes of beta cyclodextrin.
Moreover the natural air humidity and the humidity of the absorbent article may trigger the release of the complexed organic compound earlier than desired.
It is therefore desirable to provide articles comprising such inclusion complexes in a form which can be easily incorporated in such articles and which is protected from humidity.